EP1841986B1 - Hydraulic tensioning system - Google Patents

Abstract

A hydraulic tensioning system (10) for an endless drive (1) of an internal combustion engine (2). In an operating mode, the piston (9) of the tensioning system (10), which is supplied with a hydraulic fluid, is supported against a tensioning rail (6) with a non-positive fit, with the rail pre-tensioning the traction drive element (4). If the hydraulic fluid in the tensioning system (10) is not sufficient, the tensioning rail (6) is supported on an elastic end stop (13a) of the system (10).

Description

Field of the invention

The present invention relates to a hydraulic tensioning system according to the preamble of claim 1, and as it is known from DE 4443095A is known.

A clamping system is for example from the DE 196 31 607 A1 known. In this hydraulic tensioning system, a longer standstill of the internal combustion engine can lead to a pressure reduction in the pressure chamber of the clamping system, since hydraulic fluid escapes, with which the pressure chamber is acted upon by the pressure circulation lubrication of the internal combustion engine. At the start of the internal combustion engine, in the period until reaching the pressure build-up in the pressure chamber, the hydraulic tensioning system is not able to realize a required bias of the traction means. As a result, an increased noise level, caused by rattling or striking the traction means or a tensioning rail in connection with the traction means on the clamping system. At the same time, increased wear occurs in the starting phase of the internal combustion engine until it reaches the pressure build-up in the pressure chamber.

Background of the invention

The noise in the starting phase of the internal combustion engine in the known hydraulic tensioning systems does not meet the comfort demands made of today's vehicles. These clamping systems practice by means of a pressurized piston in the operating state a predetermined Tension on the traction means. The pretensioned in normal operation traction means, in particular a chain, reduces or eliminates a wear elongation and dampens largely occurring vibrations, which are triggered for example by the rotational nonuniformity of the internal combustion engine and introduced into the Endlostrieb. However, the known hydraulic clamping systems are not suitable to ensure a low-noise guidance of the traction means at a reduced, or insufficient pressure of the hydraulic fluid in the pressure chamber and high-frequency load surges of the traction means.

Summary of the invention

The object of the present invention is to further develop a generic hydraulic tensioning system in such a way that it ensures effective and low-noise guidance of the traction mechanism in all operating states of the internal combustion engine.

This problem is solved by the clamping system according to the invention according to claim 1.

Due to the structural design of a clamping system according to claim 1, the traction means of the traction mechanism is supported on an elastic end stop both in an insufficient pressure build-up of the hydraulic fluid as well as occurring high-frequency oscillations. This end stop forming a second damping device of the hydraulic tensioning system ensures in the starting phase of the internal combustion engine a low-noise guidance of the traction mechanism. In this case, the pressure chamber of the clamping system, which is preferably in communication with the pressure oil circulation lubrication of the internal combustion engine, not yet sufficiently filled with hydraulic fluid, whereby the piston of the clamping system no or no sufficient bias of the traction device guaranteed.

The inventive measure is advantageously avoided in the starting phase of the internal combustion engine, a large disadvantageous distance between the hydraulic tensioning system and the traction means, occurring vibrations of the traction means are effectively attenuated due to the elastic end stop on the clamping system according to the invention. Associated with this disadvantageous vibrations of the traction drive are prevented, as well as a disadvantageous, the noise-increasing rattling or hitting the chain, due to the guiding property of the elastic end stop.

In addition to an advantageous low-noise function in the starting phase, the clamping system according to the invention also provides for noise-optimized and safe guidance of the traction means for high-frequency oscillations of the endless drive in the normal operating state. The rotational nonuniformity of the internal combustion engine can lead to high-frequency vibrations of the endless drive, which also trigger a hitting or rattling of the traction device. In this case, the piston of the hydraulic tensioning system is exposed to impact loads which, depending on the kinematic viscosity of the hydraulic fluid, trigger a short-term actuating movement of the piston directed counter to the force displacement. The pushed back piston causes a relieved traction means, which bears against the elastic end stop.

In previous clamping systems, the short-term relief led to a hitting or rattling of the traction means or to a striking of the chain, for example, on the housing of the clamping system. According to the invention, the shock loads are advantageously intercepted or prevented by high-frequency vibrations of the traction mechanism, in particular the chain by the second damping system of the tensioning system according to the invention.

This results in an improved mechanical efficiency and increased fatigue strength of the traction device and thus the entire traction mechanism.

In an advantageous manner, the elastic limit stop according to the invention eliminates disadvantageous deflections of the traction means or limits their amplitudes in all operating states of the internal combustion engine that occur, which has an advantageous effect on the function and service life of the entire endless drive. In this case, the elastic end stop according to the invention represents a structurally simple component, which is inexpensive to manufacture and assemble. This results in a cost-effective solution that reduces the noise level of the traction device and thus meets today's comfort requirements.

The further damping system according to the invention, which includes an elastic end stop for a hydraulic tensioning system, operates in parallel with the hydraulic unit, but only operates in marginal areas when the hydraulic tensioning system is overridden. These include in particular the starting phase of the internal combustion engine in which no sufficient pressure of the hydraulic fluid is still constructed or high-frequency vibrations of the traction means, in which the piston enters the cylinder in the short term.

If necessary, the elastic end stop according to the invention can be retrofitted. For example, this component can be integrated as part of a vehicle inspection in already delivered vehicles. In addition to a cost-effective production and assembly of elastic end stop according to the invention requires no additional space, so that no adaptation construction is required.

Further advantageous embodiments of the invention are the subject of the dependent claims 2 to 10.

According to an advantageous embodiment of the invention, an elastic pin is provided as an end stop, which is associated with the housing of the hydraulic tensioning system. As a pin while a component is provided, whose length exceeds an exit region of the piston from the housing in a retracted end position. This ensures that, for example, in a start phase of the internal combustion engine, in the pressure chamber of the hydraulic tensioning system is still no sufficient pressure of the hydraulic fluid and thus the piston is not pressurized, the traction means is guided directly or indirectly on the end stop or abuts against this.

As an advantageous embodiment, the invention includes an elastic end stop a hollow cylindrical pin designed. This particular fixed to the housing pin surrounds the piston in the installed state while maintaining an annular gap, whereby the function of the piston is not hindered in operating states. The hydraulic tensioning system is expediently connected to a clamping or guide rail in an operative connection, which is assigned directly to the traction means. In the operating state of the internal combustion engine and a pressure build-up in the pressure chamber of the hydraulic clamping system whose piston is supported on the clamping rail.

The invention includes various design designed and positioned on the hydraulic clamping system elastic end stops. Preferably designed as a hollow cylindrical pin designed end stop is fixed to the housing. The attachment can be done for example by means of a bond. For this purpose, the respective end faces of the housing and the pin form a sufficient contact surface with which an effective bonding and permanent attachment of the end stop can be achieved.

Alternatively or additionally, it makes sense to, designed as a hollow cylindrical pin end stop, which is also referred to as a muffle, on to center a protruding from the housing of the clamping system section of the cylinder. This arrangement advantageously increases the contact surface between the pin on the one hand and the related components of the clamping system on the other hand, to achieve a permanent attachment.

A further embodiment of the invention precludes a multi-part construction of the elastic end stop. To achieve a wear-optimized end stop, this is preferably provided with a frontal reinforcement, for example a disc, which is preferably materially connected to the elastic material of the end stop. The reinforcement or the pane is preferably made of a high-strength, wear-resistant plastic, whereby a permanent guidance of the traction means is ensured in the starting phase of the internal combustion engine.

Alternatively or in addition to a front-side disc, it is still appropriate to provide the end stop with a length-limited socket. The bushing extends over a length corresponding to the dimension of the exiting portion of the cylinder from the housing. Thus, the socket can be pressed for example by means of a press fit on the protruding portion of the cylinder. The metallic bushing as well as the frontal disk are preferably connected by means of a vulcanization or an ultrasonic welding cohesively with the elastic material of the end stop.

As the material for the elastic end stop, an elastomer is preferably provided or any other suitable plastic, which is both lubricant-resistant and permanently usable in high ambient temperatures of> 150 ° C.

The invention further includes a sealed one for the hydraulic tensioning system Annular gap between the end stop and the piston. For this purpose, preferably a the end stop in the region of the central bore associated seal, the sealing lip is guided with a small radial bias on the lateral surface of the piston. This measure effectively prevents the entry of even the smallest abrasion parts in the leakage gap, which is established between the piston and the cylinder wall. On the other hand, the sealing lip does not affect the damping device when hydraulic fluid is deactivated via the leakage gap.

Brief description of the drawings

Figur 1:

einen Endlostrieb im eingebauten Zustand, in Verbindung des erfindungsgemäßen hydraulischen Spannsystems;

Figur 2:

eine Schnittdarstellung des erfindungsgemäßen Spannsystems in einer 3 D-Ansicht;

Figur 3

ein erfindungsgemäßes Spannsystem im Längsschnitt.

Various embodiments of the invention are illustrated in the figures. Show it:

FIG. 1:

a Endlostrieb in the installed state, in conjunction of the hydraulic tensioning system according to the invention;

FIG. 2:

a sectional view of the clamping system according to the invention in a 3-D view;

FIG. 3

an inventive clamping system in longitudinal section.

Detailed description of the drawings

The FIG. 1 shows a detail of a Endlostrieb 1, which is designed as a chain drive of an internal combustion engine 2. Designed as a control drive Endlostrieb 1 is used to drive the camshaft of the engine 2, in FIG. 1 are not shown. The drive is effected by the rotating in a clockwise direction, with the crankshaft of the internal combustion engine 2 in connection drive wheel 3 via a traction means 4, a chain on the in FIG. 1 not shown, with camshafts of the engine 2 in connection with other sprockets. In Zugtrum the Endlostriebs 1, the traction means 4 is guided on a guide rail 5. The slack side of the traction means 4 is associated with a tensioning rail 6, which is pivotable about an axis of rotation 7. Spaced to the axis of rotation 7 of the clamping rail 6 is associated with a hydraulic clamping system 10, the pressurized, the tensioning rail 6 pivoted clockwise and thereby biases the traction means 4. The hydraulic tensioning system 10 is fixed in position with a housing 8 on the internal combustion engine 2. For pressurizing a piston 9 integrated in the housing 8, a pressure chamber 11 of the clamping system 10 communicates with a pressure circulation lubrication of the internal combustion engine 2. In addition, the piston 9 is spring-loaded by means of a pressure spring 11 inserted in the pressure chamber 11, which always presses the piston 9 with a relatively small preload against the tensioning rail 6.

At standstill of the internal combustion engine 2, there is a drop in the oil pressure of the pressure circulation lubrication, associated with a loss of hydraulic fluid of the hydraulic clamping system 10, whereby the piston 9 rests only with the force of the compression spring 12 on the tensioning rail 6. At a restart of the internal combustion engine 2, up to a pressure build-up in the pressure chamber 11, the traction means 4 is not sufficiently biased, resulting in large oscillations of the traction means 4 in conjunction with actuating movements of the tensioning rail 6. In this case, the spring-loaded piston 9 is pushed back, whereby the clamping rail 6 strikes or is supported on an elastic end stop 13a. This measure reduces the noise of Endlostriebs 1 in the starting phase which simultaneously reduces the wear of the piston 9 and the clamping rail 6 in the region of a contact surface 14 of these components.

The FIG. 2 illustrates more details of the hydraulic clamping system 10. The example, rotationally symmetrical designed housing 8 is provided with a central blind hole 15, which is for receiving a cylinder 16 is determined. The designed as a sleeve cylinder 16 serves to receive the piston 9, wherein the components, the cylinder 16 and the piston 9 define the pressure chamber 11. To this end, the cylinder 16 has a spring-loaded one-way valve 18 which separates the pressure chamber 11 from a reservoir 19, which encloses the cylinder 16 locally and integrated in the housing 8, for the hydraulic fluid. When pressure is applied to the storage space 19 by means of a supply bore 17 introduced in the housing 8, the hydraulic fluid passes via the one-way valve 18 into the pressure chamber 11 and displaces the piston 9 until it bears against the tensioning rail 6 by force.

When occurring peak forces that are transmitted, for example, by impact shocks of the traction device 4 on the clamping rail 6, the piston 9 is additionally loaded against the direction of the arrow. Thereby, a subset of the hydraulic fluid is controlled via the damping device 32, which is formed from a leakage gap 20 between the lateral surface of the piston 9 and an inner wall of the cylinder 16. The escaping hydraulic fluid can, for example, flow back without pressure into the oil sump inside the internal combustion engine 2. Already after a slight lifting movement against the direction of the arrow, the in FIG. 1 shown clamping rail 6 on the end face 21 of the elastic end stop 13a from, the second damping device 33, whereby an adverse noise development is omitted.

The FIG. 3 shows, in particular, inventive design variants of the end stop 13b. For fixing the position of the end stop 13b on the housing 8, in particular a bond between the end faces of the housing 8 and the end stop 13b, which together form a contact surface 22, is suitable. Furthermore, the end stop 13 b is centered on a portion 23 of the cylinder 16, which emerges from the housing 8 and simultaneously guides the piston 9. For improved fastening, an armored end stop 13b is provided for this purpose, which includes a bushing 24, preferably made of steel, which is pressed onto the section 23 of the cylinder 16.

Furthermore, the end stop 13b includes a wear-optimized disk 25 on the front side, on which the tensioning rail 6 is supported in the starting phase of the internal combustion engine 2. The disk 25 is preferably made of a wear-resistant, such as a glass fiber reinforced plastic. Coincidentally, the bush 24 and the disk 25 are materially connected to the rest of the elastic body of the end stop 13b. For this purpose, for example, a vulcanization or ultrasonic welding is suitable. The end stop 13b also comprises, in order to achieve a sealed annular gap 26, which is established between the piston 9 and the end stop 13b, a seal 27, the sealing lip 28 abuts against the lateral surface of the piston 9 with a small supporting force. On the one hand, the sealing lip 28 prevents disadvantageous entry, for example of oil foam, into the annular gap 26 and, on the other hand, allows unimpeded functioning of the damping device 32, ie. a Absteuern the hydraulic fluid through the leakage gap 20 at a piston stroke in the direction of the one-way valve 18th

The FIG. 3 shows the piston 3 of the hydraulic tensioning system in the operating position, in which the acted upon by the pressure of the hydraulic fluid piston 9 at the in FIG. 1 pictured clamping rail 6 is supported non-positively. This results in a stroke "s" between the end faces of the piston 9 and the end stop 13b. The maximum travel of the piston 9 relative to the cylinder 16 is limited by a retaining ring 29 which is inserted with a partial cross-sectional area in an annular groove 30 of the piston 9 and the outer contour is guided in a length-limited recess 31 of the cylinder 16.

LIST OF REFERENCE NUMBERS

1.

endless drive

Second

Internal combustion engine

Third

drive wheel

4th

traction means

5th

guide rail

6th

tensioning rail

7th

axis of rotation

8th.

casing

9th

piston

10th

clamping system

11th

pressure chamber

12th

compression spring

13 a.

end stop

13 b.

end stop

14th

contact area

15th

drilling

16th

cylinder

17th

feed bore

18th

one-way valve

19th

pantry

20th

leakage gap

21st

face

22nd

contact area

23rd

section

24th

Rifle

25th

disc

26th

annular gap

27th

poetry

28th

sealing lip

29th

circlip

30th

ring groove

31st

recess

32nd

attenuator

33rd

attenuator

Claims (10)

1. Hydraulic tension system for an endless drive (1), in particular chain drive of an internal combustion engine (2), with a housing (8) for receiving a cylinder (16), in which is guided longitudinally movably a sprong piston (9) which is acted upon by a hydraulic fluid and cooperates with a traction means (4) and which together with a cylinder (16) delimits a pressure space (11) filled with a hydraulic fluid, there being provided, for the damping of actuating movements of the piston (9), a damping device (32) at which a part-quantity of the hydraulic fluid can be discharged out of the pressure space (11) via at least one leakage gap (20), and, in the event of a pressure drop and/or high-frequency oscillations of the endless drive (1), the traction means (4) being supported indirectly or directly on an elastic limit stop (13a, 13b), forming a second damping device (33), of the hydraulic tension system (10), characterized in that a tenon of hollow-cylindrical configuration, assigned to the housing (8) of the tension system (10) and projecting with respect to a retracted position of the piston (9), forms the elastic limit stop (13a, 13b).
2. Tension system according to Claim 1, in which, in a starting phase of the internal combustion engine (2), the limit stop (13a, 13b) cooperates indirectly or directly with the traction means (4).
3. Tension system according to Claim 1 or according to Claim 2, on which, in the operating state, the traction means (4) cooperates indirectly with the tension system (10) in that a tension rail (6) is supported on the piston (9).
4. Tension system according to one of Claims 1 to 3, the limit stop (13a, 13b) configured as a tenon being fixed in position on the housing (8).
5. Tension system according to one of Claims 1 to 4, in which the limit stop (13a, 13b) is centred on a portion (23), emerging from the housing (8), of the cylinder (16) and is supported on the end face on the housing (8).
6. Tension system according to one of Claims 1 to 5, which comprises a limit stop (13b) which has a multi-part construction and which forms a damping device (33).
7. Tension system according to Claim 6, the elastic limit stop (13b) of which encloses on the end face a disc (25) which is preferably produced from a wear-resistant plastic and which, particularly in a starting phase of the internal combustion engine (2), cooperates with the tension rail (6).
8. Tension system according to Claim 6, in which the limit stop (13b) encloses a bush (24) of limited length which is produced from a metallic material and is fastened to the housing (8) and/or to the cylinder (16) and which is connected in the materially integral manner to the elastic body of the limit stop (13b).
9. Tension system according to one of Claims 1 to 8, the elastic limit stop (13a, 13b) of which is produced from an elastomeric material.
10. Tension system according to one of Claims 1 to 9, the limit stop (13b) comprising a seal (27) which is inserted in an annular gap (26) delimited radially by the piston (9) and the limit stop (13b) and the sealing lip (28) of which is supported sealingly on a surface area of the piston (9).

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